Endpoints such as Internet Protocol (IP) phones can make multimedia communications such as Voice over IP (VoIP) calls over a packet switched network using multimedia session signaling protocols such as Session Initial Protocol (SIP). Security devices such as firewalls and Network Address Translators (NATs) located between two endpoints can prevent the flow of multimedia messages between the two endpoints. Simple Traversal of User Datagram Protocol (UDP) Through NATs (STUN) was developed to allow multimedia communications to operate through NATs, STUN is described in Request for Comment (RFC) 3489.
STUN is used by a calling device to determine a NAT public address and NAT port number associated with the calling device. The calling device provides the NAT public address and NAT port number to the target endpoint during a call establishment process. The use of STUN as described in RFC 3489 when more than one NAT or any amount of firewalls are interposed between a calling device and the Internet produces certain inefficiencies and problems. The disclosure that follows solves these and other problems.